The present invention relates to shoe soles of training shoes, walking shoes, business shoes, casual shoes and the like which can apply a larger-than-normal load to leg muscles and strengthen the lower half of the body of the wearer of the shoes while the wearer of the shoes is walking or otherwise exercising.
Conventional training shoes for strengthening the lower half of the body during walking are provided with a weight and the like embedded in soles to increase the overall weight of shoes. For example, U.S. Pat. No. 5,231,776 discloses a shoe having a weight-retaining matrix of lattice grid structure molded to a sole, each matrix being filled with metallic balls. Instead of such metallic balls, a shoe disclosed in U.S. Pat. No. 5,758,435 is provided with a shoe sole having weight chambers which are filled with the weights comprising a mixture of metallic grains and adhesives.
However, in the above conventional shoes, the operations of filling metallic balls or weights into a large number of matrixes or chambers are extremely troublesome. Furthermore, when the weight of the metallic balls or weights varies in each matrix or chamber, the overall balance of shoe soles is destroyed and walking comfort deteriorates.
In Japanese Utility Model Publication No. 45-21005, there is disclosed a shoe having a shoe sole comprising an outsole, a midsole and an insole wherein a plurality of recesses are formed on the upper surface of the midsole in the width direction of the sole and parallel to one another in the lengthwise direction of the sole and weights are embedded in the recesses. The weights comprise a mixture of resilient materials such as natural rubber, synthetic rubber or synthetic resin etc. and metallic grains. In manufacturing such a shoe, the weights should be made in conformity with the concave form of the recesses and each weight should be embedded in a corresponding recess of the same form. Thus it is extremely troublesome to embed the weights and the workability is poor.
Furthermore, in Japanese Utility Model Application laid-open under No. 56-103205, there is disclosed a shoe having a shoe sole provided with a recess at the toe portion and at the heel portion respectively and provided with a metallic weight embedded in the respective recess. In this construction, embedding the weights is comparatively easy. However, when the weight difference is large between the two weights, the weight balance of the shoe is destroyed and eventually an excessive load is applied to legs of the wearer of such shoe, and as a result, the shoe may cause bodily injury instead of strengthening the lower half of the body of the wearer. In addition, since the weight is made of metal and is not flexible, walking comfort deteriorates.
As mentioned above, conventional shoes in any structures have merits and demerits. It is therefore an object of the present invention to provide a shoe sole having good overall weight balance and flexibility suitable for walking, while improving the operational efficiency of embedding weights.
According to the present invention, there is provided a shoe sole including a resilient outsole having a single recess bored on the upper surface and extending in the lengthwise direction from a toe portion to a heel portion of the outsole. The recess has a similar outline to the outline of the outsole, and a single weight comprising a mixture of a resilient material and metallic grains is embedded in the recess.
In such a shoe sole, the single weight can be easily embedded in the single recess bored on the upper surface of the outsole after being prepared in a separate manufacturing process, and the workability of embedding the weight is improved. Since the weight is formed with a mixture of a resilient material and metallic grains, it has resilience to function as a shock absorber, so that there is no need to adopt such shock absorbing materials such as rubber sponges and the like. The metallic grains are made of iron, stainless steel or the like having a large specific gravity and may be granular, powder or flake in shape.
It is preferred that the single weight has a similar outline to the outline of the outsole and fits in the recess having a similar outline to the outline of the outsole, so that the weight can be easily disposed at a well-balanced position in the outsole and that the load of weight applied to the sole disperses widely. It is then possible to maintain a proper weight balance of the shoe sole. The resilient weight deforms when a load is applied thereto, but as the recess is formed to fit over the entire sole of a foot, the deformation of the weight occurs uniformly, so that weight balance is maintained when the a load is applied the shoe sole.
It is also preferable that the weight is formed so as to be thin at the toe portion and thick at the heel portion, so that the weight can be easily bent from the toe portion. Thus, the flexibility of the outsole is maintained inspite of the existence of the weight. As the heel portion is formed so as to be thick, it receives firmly the heel of the foot without causing excessive deformation.
Also, it is preferred that the weight comprises a resilient housing and a mixture of a resilient material and metallic grains filled in the housing.
There is also provided a shoe sole comprising a resilient outsole having a single recess bored on the upper surface and extending in the lengthwise direction from a toe portion to a heel portion of the outsole and a single weight comprising a resilient housing and a mixture of a resilient material and metallic grains filled in the housing. The recess has a similar outline to the outline of the outsole, and the single weight has a similar outline to the outline of the outsole and fits in the recess. The weight is formed so as to be thin at the toe portion and thick at the heel portion with an upper surface that is level with an upper surface of the outsole.
In case the upper surface of the weight is level with the upper surface of the outsole, shoe components to be superposed on the outsole are stably set without causing gaps therebetween, so that the durability of the shoe is increased and no strange feelings are experienced by the wearer.
Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which: